Arthroplasty is an operation to restore as far as possible the integrity and functional power of a joint. An artificial joint is created for example to correct advanced degenerative arthritis.
A conventional method for treatment of severe arthritis of the hip involves performing an internal amputation of the proximal end 11 of the femur 10 (see FIG. 1), and its replacement with an appropriately shaped metallic device. A spacer or grouting agent, such as for example methyl-methacrylate (bone cement) is used to seat and secure the metal implant into the femur. This is called primary total hip arthroplasty.
After several years, the metal implant needs to be replaced by a new one. The grouting agent (bone cement) needs to be removed from the femoral canal. This is a particularly problematic, lengthy and tedious procedure. It can be associated with severe complications like perforation of the femoral canal or femoral fractures (with a rate of up to 18%). Numerous devices have been advocated to facilitate cement removal.
Traditionally actions within the marrow canal of the bone in primary and revision hip arthroplasty have been performed blindly. Problems encountered were that sizing of the femoral stem was not always accurate, and that the canal was not always dry before placing the metallic implant. In revision hip arthroplasty it was very difficult to remove the grouting agent (cement), especially distally in the femoral canal.
Intramedullary bone endoscopy, intraosseus endoscopy, bone marrow endoscopy and medulloscopy are synonyms to describe a more recently used visual inspection method and system of the medullary canal. Medulloscopy, a term first introduced by Roberts, means endoscopic visual inspection of the intramedullary canal of a long bone. Most of the clinical experience so far focuses on endoscopically assisted cement removal in revision hip arthroplasty. Endoscopy has also been used to assist pedicle screw placement, core decompression, autogenous bone grafting, canal preparation in primary hip arthroplasty and inspection of the medullary canal in septic nonunions of long bones.
Several devices have been proposed. One solution is provided by M. Porsch (OrthoScope, available from Swiss OrthoClast) in 1999 (OrthoScope, available from Swiss OrthoClast) and provides a rigid camera system 21 and a separate chiseling system 22. It is a disadvantage of the endoscopic resection system of FIG. 2 that the camera system, in view of its long straight arm 23 and heavy camera part 24, requires manipulation with two hands, which implies that it has to be manipulated by an assistant. Furthermore, a scope based on Hopkins-lenses always has to be of a well-defined length and is always straight because of the optical physics of this type of lenses, although the femoral shaft is somewhat bowed. The shape of the femoral canal as well as its diameter differ from patient to patient. Such stiff scope cannot be deformed and is very vulnerable, especially when being in close proximity with the chiseling system 22. As such, a good view with the scope, deep down the shaft, cannot be obtained.
Another solution is provided by M. Oberst in 2002 (Intramedullary bone endoscopy—IBE) and is illustrated in FIG. 3a and FIG. 3b. A hollow rigid tube 31 is introduced into a bone canal. The rigid tube 31 is at its front extremity provided with a camera system 32 (Hopkins lens). Instruments, such as for example a grasping forceps 33 and a suction tube 34, are introduced into the rigid tube 31. A disadvantage of this solution is that it has limited ergonomy.